Guilford is a town in New Haven county in Connecticut. It was formed in 1643 from the following town or towns: . Guilford is a part of the Guilford probate district and has been since 1719. New Haven/New London was/were the previous chronological district or districts. For more information, contact the county at 31 Park St. Guilford 06437-2629. On the attached map, New Haven is located at E6.